1. Field of the Invention
The present invention relates to an ink-jet ink, and a recording method, a recording unit, an ink cartridge, and a recording apparatus using the ink. In particular, the present invention relates to an ink-jet ink that does not cause clogging in an ejection orifice portion and deposition of a coloring material and is capable of providing good print quality without ink bleeding even after leaving an image printed on coated paper or the like having an ink-receiving layer for a long term under high temperature and humidity conditions. In particular, the inventions also relates to a recording method, a recording unit, an ink cartridge, and a recording apparatus using the ink.
2. Related Background Art
An ink-jet recording method is for performing recording on a recording medium such as paper by allowing small ink droplets to adhere to the recording medium. There has been a desire for the ink to be used in such a recording method to have characteristics suitable for the ink-jet recording apparatus, such as high storage stability, a lack of clogging in an ejection orifice, no deposition of a coloring material, and excellent ejection stability.
Conventionally, the use of an aqueous ink as an ink for ink-jet recording has occasionally resulted in troubles such as a clogged nozzle due to moisture exuding from the ink supplied from a recording head. To solve this problem, it has been reported that the use of a dissolution auxiliary agent in an ink is effective to improve the solubility of a water-soluble coloring material in the ink even after water evaporates from the ink (see, e.g., Japanese Patent Application Laid-Open Nos. H06-025573, H08-120204, and H09-095637). The dissolution auxiliary agent added may be a certain amount of a water-soluble organic solvent capable of dissolving a large amount of a coloring material or urea or a derivative thereof with an excellent moisture-retaining property.
However, when an image is recorded on a so-called coated paper prepared by forming an ink-receiving layer containing a pigment and a binder on a substrate such as paper, in accordance with an ink-jet process using a water-soluble organic solvent capable of dissolving a large amount of a coloring material or urea or a derivative thereof having an excellent moisture-retaining ability, a decrease in print quality may occur because of ink bleeding caused after leaving the image for a long term under certain environmental conditions, in particular, under high temperature and humidity conditions (hereinafter the ink bleeding under such conditions will be also referred to as the “ink bleeding at high temperature and humidity”).